In fact, OpenBSD is not installed on this computer anymore. I couldn't get cpu scaling to work on it with 4.9. (Didn't try very hard though).

I wanted to see if it worked with 5.0 when I booted from the install disk (install50.iso).
The thing is I first downloaded the i386 version because I aimed to install OpenBSD on a usb stick to then install to my i386 netbook.
From this cd I had the error I posted.

Then I tried again with the amd64 version to find that apmd is not in /sbin.

I wanted to post the dmesg output, but I have first to find how to mount an ext2fs (or whatever works) drive from the installation disk shell.